Kay Kay Menon was the first choice for the lead role (K), but he declined suggesting Kashyap to cast an actor having stardom. Anurag then offered SRK the role, who ultimately declined as he felt that the movie promotes 'anti-smoking' feelings. John Abraham was the only star-actor to love the script, and agree to do it.
John Abraham who quit smoking, had to smoke 99 cigarettes a day to get into the character which resulted in his lungs getting affected.
Anurag Kashyap's then-assistant Vikramaditya Motwane (later director of Udaan) appears in a shot where he shows us the middle finger, smoking a cigar in John Abraham's office right after John passes an order to ban the smoking in his office. The resignation letter is shown to be written by Vikramaditya Motwane.
About halfway through the film one character says a dialogue, while launching his cigars in India, which goes like "'Beedi Jalaai le' ke is 'vishal' desh mein, cigar 'gulzar'" (In this 'Vishal' (huge) country of 'Beedi jalaai le' (smoking), cigar is 'Gulzar' (flourishing or pleasant)). This dialogue is a cleverly put tribute to the following: Vishal Bhardwaj - the music director and producer of this film (and a good friend of Anurag Kashyap), the lyrics writer of the film Gulzar (a close friend of both Vishal Bharadwaj and Anurag Kashyap) and the song 'Beedi Jalaai Le' from Vishal's then recently released movie Omkara (2006)